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Fetal Elastic Cartilage

As with bone, elastic cartilage contains a matrix, fibers, and cells. In human elastic cartilage, the cartilage cells (chondrocytes) are contained in lacunae and the matrix contains abundant elastic fibers, explaining the characteristic flexibility of this type of connective tissue.

Providing flexible support to the human ears, the auditory canals, and the epiglottis, elastic cartilage is structurally identical to the more common hyaline cartilage except that it contains, in addition to Type II collagen fibers, a dense network of branching and anastomosing elastic fibers. Type II collagen fibers are composed predominantly of chondroitin sulfates and hyaluronic acid, with lesser amounts of keratin sulfate and herparin sulfate. Glycoproteins, the glue that holds the matrix together, include link proteins, fibronectin, chondronectin, and tissue fluid. At the core of the elastic cartilage mass, the network is at its densest. Surrounding and nourishing the elastic cartilage mass is the perichondrium, and unlike hyaline cartilage, the chondrocytes are found in isogenous groups.

Elastic cartilage develops from a primitive type of connective tissue, which contains wavy bundles of fibrils that are neither elastin nor collagen. Fibroblasts secrete elastin in the fetus and the fiber bundles branch, and are cross-linked, creating a gel-like consistency. As with hyaline cartilage, the fetal tissue chondrocytes differentiate with the chondroblasts at the center, first secreting matrix material, which then separates into the individual cells. During embryonic development, mesenchymal cells retract their cytoplasmic extensions and assume the rounded shape of chondroblasts. As they become tightly packed, the increased cell-to-cell contact stimulates cartilage differentiation, progressing from the center outwards to the periphery of the fetal tissue.